If the image in your PDF file looks dark when viewed on Adobe Acrobat Reader, it is because of a particular setting. To resolve this issue, follow the steps below:
- Open your PDF file on Adobe Acrobat Reader.
- Click on Edit.
- Click on Preferences.
- Select Page Display from the list of categories.
- Under Rendering, make sure that the check box beside Enhance thin lines is unchecked.
- Click OK.
- Try reopening your PDF file again. The image in the PDF file should be fine now.